In order to form a basis for understanding the detailed mechanism of oxygen transport in biological systems, we wish to determine, by single crystal x-ray diffraction techniques, the structures of several artificial oxygen-carrying chelates of cobalt. It is presently feasible to determine the geometry and interatomic distances at the site of oxygen binding with a high degree of accuracy in these molecules; such is not the case for, say, hemoglobin. This research will involve the preparation of single crystals of oxygenated and un-oxygenated forms of bis (salicylaldehyde) ethylenediimine cobalt (II), bis (3- fluorosalicylaldehyde) ethylenediimine cobalt (II), bis (histidine) cobalt (II), and other such chelate compounds. Complete x-ray data will be collected for such of these compounds as form suitable crystals and these data will be analyzed to determine the crystal and molecular structures of the compounds.